The present invention relates to a liquid ejection apparatus for ejecting liquid as droplets with a liquid ejection head, such as an inkjet recording apparatus, a display manufacturing apparatus, an electrode formation apparatus, or a biochip manufacturing apparatus, and to a method for controlling such a liquid ejection apparatus.
An inkjet recording apparatus is known in the prior art as a liquid ejection apparatus that ejects liquid droplets from a nozzle of an ejection head. One type of such an inkjet recording apparatus (hereafter referred to as a “recording apparatus”) includes a main tank located apart from its carriage and is referred to as an off-carriage type recording apparatus.
Such type of an inkjet recording apparatus may be used for business purposes. To print in relatively large quantities, a business purpose inkjet recording apparatus includes a plurality of large-capacity main tanks and sub tanks corresponding to the main tanks. The sub-tanks are arranged on a carriage, which includes a recording head functioning as an ejection head. Ink is supplied from each main tank to the corresponding sub tank via an ink supply tube and then to the recording head from the sub tank.
A large-size recording apparatus having a long carriage scanning distance is designed for performing printing on large papers. To improve the throughput, the recording head of a large-size recording apparatus includes an increased number of nozzles. The recording apparatus needs a plurality of ink supply tubes corresponding to a plurality of colors of ink to connect its main tanks to sub tanks, which are arranged on the carriage. Due to the long carriage scanning distance of such a recording apparatus, the ink supply tubes connecting the main tanks and the sub tanks are inevitably long. Further, due to the increased number of nozzles in the recording head, the recording apparatus consumes a large amount of ink. As a result, the kinetic pressure of ink in each ink supply tube connecting the main tank and the sub tank increases. This may cause the amount of ink supplied to each sub tank to become insufficient.
An inkjet recording apparatus having a structure for supplying a sufficient amount of ink to each sub tank has been proposed. This inkjet recording apparatus applies air pressure to each main tank, and generates a forced flow of ink from each main tank to each sub tank.
Such type of a recording apparatus includes an air pressurization pump, which applies pressurized air to each main tank, and a pressure detector, which detects the air pressure applied to each main tank. Based on a control signal provided from a host computer, the recording apparatus drives or stops the air pressurization pump in accordance with the pressure detected by the pressure detector during printing, nozzle cleaning, or flushing. This supplies a sufficient amount of ink to each sub tank during printing, nozzle cleaning, or flushing.
When waiting for input of a control signal during a standby state, the recording apparatus drives or stops the air pressurization pump based on the pressure detected by the pressure detector. As a result, a sufficient amount of ink is supplied to each sub tank even during a standby state.
Peripherals connected to the host computer conventionally are provided with functions for entering a power saving control mode (low power consumption mode) to reduce power consumption. The peripherals shift to the power saving control mode when a standby state in which no control signal is input from the host computer continues for at least a predetermined time or when a command to shift to the power saving control mode is provided from the user.
The power saving control mode is specified in detail by the Energy Star standard.
Japanese Laid-Open Patent Publication No. 2004-255658 describes a power saving control mode based on the Energy Star standard but does not mention an air pressurization pump. Japanese Laid-Open Patent Publication No. 10-193628 describes a sleep mode and a refresh operation but does not mention the driving of an air pressurization pump system. Japanese Laid-Open Patent Publication No. 8-310082 describes a power saving function of a printer but does not mention the driving of an air pressurization pump system.
The prior art recording apparatus described above drives or stops the air pressurization pump based on the pressure detected by the pressure detector when waiting for an input of a control signal from the host computer during the standby mode. With this structure, when the recording apparatus is not receiving a control signal instructing printing or other operations from the host computer and the air pressurization pump is not being driven, the air pressure may decrease before a predetermined time for waiting for input of a control signal elapses during the standby state. In this case, the decreased pressure is detected by the pressure detector, and the air pressurization pump is driven based on the detected pressure.
In this manner, the pressure detector and the air pressurization pump does not always operate in a coordinated manner in the prior art. Thus, power-reduction measures have not been taken in this respect.
As a result, the recording apparatus including the prior art air pressurization pump does not satisfy the requirements for a power saving control mode.
The recording apparatus is given above as an example. However, the problem of failing to satisfy the power saving control occurs in other liquid ejection apparatuses that eject liquid droplets with a liquid ejection head when an air pressurization pump is driven based on the detected value of a pressure detector during a standby state. Examples of such other liquid ejection apparatuses include a display manufacturing apparatus, an electrode formation apparatus, and a biochip manufacturing apparatus.